samples: drivers: espi: Showcase eSPI host warnings handling

Add sample of how to handle eSPI host warnings when these are
intercepted by app code.
Replace printk with logging macros to standardize the sample.
Log additional details about peripheral channel notifications.
Remove unnecessary trailing \n from logging messages.

Signed-off-by: Jose Alberto Meza <jose.a.meza.arellano@intel.com>